The human eye contains three types of color receptors (these are sometimes called red-absorbing cones, green-absorbing cones and blue-absorbing cones). These color receptors each respond to light over a wide range of visible wavelengths. Each of the types of receptor is most sensitive at a different wavelength. Red-absorbing cones typically have a peak sensitivity at roughly 565 nm. Green-absorbing cones typically have peak sensitivity at roughly 535 nm. Blue-absorbing cones typically have a peak sensitivity at roughly 440 nm. This arrangement is illustrated schematically in FIG. 1. The sensation of color perceived by a human observer when light is incident upon the observer's eye depends upon the degree to which each of the three types of receptor is excited by the incident light.
Conveniently, the human visual system (“HVS”) does not distinguish between light of different spectral compositions that causes the same degree of stimulation of each of the different types of color receptor (e.g. light having different spectral power distributions that have the same tristimulus values). A sensation of any color within a gamut of colors can be created by exposing an observer to light made up of a mixture of three primary colors. The primary colors may each comprise only light in a narrow band. Many current displays use different mixtures of red, green and blue (RGB) light to generate sensations of a large number of colors.
Saturation is a measure which takes into account intensity of light and the degree to which the light is spread across the visible spectrum. Light that is both very intense and concentrated in a narrow wavelength range has a high saturation. Saturation is decreased as the intensity decreases and/or the light contains spectral components distributed over a broader wavelength band. Saturation can be reduced by mixing in white or other broad-band light.
Patent literature in the field of color display includes:
U.S. Pat. Nos. 7,397,485; 7,184,067; 6,570,584; 6,897,876; 6,724,934; 6,876,764; 5,563,621; 6,392,717; 6,453,067;
US patent application No. 20050885147; and,
PCT publication Nos. WO2006010244; WO 02069030 and WO03/077013.
There is demand for displays capable of accurately and consistently representing colors. There is a need for displays, display components and associated methods which can facilitate providing high quality color images.